Merge pull request #26590 from Kumataro:fix26589

Support C++20 standard #26590

Close https://github.com/opencv/opencv/issues/26589
Related https://github.com/opencv/opencv_contrib/pull/3842
Related: https://github.com/opencv/opencv/issues/20269

- do not arithmetic enums and ( different enums or floating numeric) 
- remove unused variable

### Pull Request Readiness Checklist

See details at https://github.com/opencv/opencv/wiki/How_to_contribute#making-a-good-pull-request

- [x] I agree to contribute to the project under Apache 2 License.
- [x] To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
- [x] The PR is proposed to the proper branch
- [x] There is a reference to the original bug report and related work
- [x] There is accuracy test, performance test and test data in opencv_extra repository, if applicable
      Patch to opencv_extra has the same branch name.
- [x] The feature is well documented and sample code can be built with the project CMake

modules/core/src/matrix_sparse.cpp

@@ -171,7 +171,14 @@ void SparseMat::Hdr::clear()
     hashtab.clear();
     hashtab.resize(HASH_SIZE0);
     pool.clear();
+#if defined(__GNUC__)  && (__GNUC__ == 13) && !defined(__clang__) && (__cplusplus >= 202002L)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wstringop-overflow"
+#endif
     pool.resize(nodeSize);
+#if defined(__GNUC__)  && (__GNUC__ == 13) && !defined(__clang__) && (__cplusplus >= 202002L)
+#pragma GCC diagnostic pop
+#endif
     nodeCount = freeList = 0;
 }